HPMoR: The Missing (but Necessary) Chapters
by qbsmd
Summary: An extension of the universe of "Harry Potter and the Methods of Rationality". Includes scenes that should have been but weren't. They contribute nothing to the plot or explaining the universe, but answer important questions that may otherwise never be answered.
1. Playing with Fire

Chapter 21 3/4: Playing with Fire

It was late September and the students had largely acclimated to the strange school. There was no quidditch game for this weekend and no extra-curricular activities had started up yet. It was Saturday, so there was, of course, no danger of anyone attempting to do homework. They were, in a word, bored.

"Even my first memory is my mother yelling", Ron continued. "Small objects around the house would always disappear, like one of a pair of shoes or socks, or some silverware. They'd eventually show up somewhere weird like the back of a random closet or on the roof. This started before Fred and George pranked everyone all the time, so my parents had assumed it was a ghost. Eventually, my parents figured out it was the twins' accidental magic. After that, everyone would yell at them every time they couldn't find something."

"So why don't you tell them about the first time you used accidental magic?" Fred asked from behind Ron, making him jump in surprise.

"It's an amusing, though not unexpected, story for anyone who knows you" said George.

"It's not that amusing" Ron protested.

"As I recall, he was about nine..."

"More like eight."

"...when we were eating dinner, like any other evening."

"And then mum noticed he hadn't finished any of his meat or vegetables..."

"Even though he'd been eating..."

"Rather quickly..."

"...the entire time we'd been sitting down."

"It was quickly discovered that his chicken was spontaneously leaking chocolate sauce."

"And he'd been spooning it into his mouth as fast as it appeared."

"Apparently producing food is really rare for accidental magic..."

"Unless someone is malnourished or starving."

"...otherwise most kids would always have sweets."

"We learned this after a medical person told mum to make sure he was eating enough..."

"After she told the story at our next checkup."

"It's the only time I've ever seen her embarrassed."

"What about you Neville?" Ron quickly tried to change the subject.

"Uh, my story's not that interesting."

"Mine is," Dean jumped in excitedly. "We were at the zoo and my annoying cousin was being annoying. Then while he was leaning against the glass watching a snake, the glass became intangible, so he fell through it, and then it restored itself with him trapped inside. The snake had wrapped around him a few times before the zoo people got him out. And then the ministry had to obliviate soooo many people. Like a couple dozen people were watching, and then they called in like half the employees when he was in the cage. And then they all wandered off and told other people before the aurors got there about ten minutes later. But it was awesome and my cousin wasn't as annoying after that."

"Harry, Hermione, hey!" called Fred.

"We wanted to ask you something...", George added.

"We were talking about everyone's first accidental use of magic. What were yours?"

Harry slowed down and answered "I've never used accidental magic."

Hermione quickly added "neither have I."

"You're both lying" George accused.

"Guess how we know" Fred challenged.

Harry stopped and made eye contact with both of them while responding. "If muggleborns didn't use accidental magic then no one would ever know about them, and I wasn't lying."

"Well, half of that is true..." George began.

"But we'll come back to that in a moment. Hermione, spill." Fred interrupted.

"And we have auror connections, so if you don't tell us, we'll find out anyway. And then so will everyone." George added with an evil smile.

"Ugh, fine. The first day of second grade, someone started making fun of me, then suddenly stopped talking. They had to take her to a hospital after they realized her lips were super-glued together."

"So you literally shut her up; that's actually pretty cool", Harry said. "And super-glue is the perfect weapon for bullies: it's non-lethal but can still be a serious deterrent."

Ron frowned at Harry and opened his mouth but Ernie spoke first, "Why would muggles do that; it's not like they know about blood purity- Ow! Don't kick me under the table, you... freckled chocolate sucker."

"You were being a bloody- wait, what did you call me?"

"It's a Hufflepuff insult" Fred replied.

"They pretty much all sound like that" George added.

"And now it's your turn, Harry."

"You want me to make something up? You probably wouldn't believe it; my life's typically weirder than any story I could tell."

"Alright, Harry. If you're sticking with that story, we'll just tell everyone what we know," Fred shrugged

"You can jump in whenever you're inspired," George encouraged.

"No, go ahead with your story. I'm sure it will be entertaining, though fictional."

"You were going to a muggle school, like Hermione."

"Until you almost burned it down."

"The muggles sent five big, loud, red things that spit water and carry fire-stopping people."

"Which is apparently a big deal. Normally one is supposed to be enough."

"And then the aurors had to modify their memories so the fire didn't look magical."

Harry sighed. "Surprisingly, about half of that is true," he began. "I went to a muggle school, there was a fire, and they did send five fire engines before getting it under control. And everyone blamed me, even though it was, at most, 10% my fault. I was a lot younger then and nowhere near as knowledgeable or responsible as I am now."

He paused briefly as everyone around the table smirked or snorted. "It all started when the teacher announced that we were having a 'science fair', which basically involves everyone doing a project and explaining it to random people. The normal intention is for students to pick a topic they want to understand better and answer some related question using the scientific method. Unfortunately, we were considered too young for that, so we were assigned pre-determined projects. Not that I knew all of this at the time."

He looked around and saw mostly confusion. "The projects were things like connecting potatoes together with bits of metal to make electricity or doing pointless things with magnets or other things that sounded vaguely sciency. Then the teacher mentioned something about volcanoes and I had to interrupt, because the only thing I had known about volcanoes was that they erupted molten rock and destroyed everything around them. This sounded quite dangerous to me, so I pointed that out and asked where this science fair would take place. Her response was that they would put down a tarp and everything would be okay. I noticed I was confused, but didn't press the issue. Unfortunately, she decided that I would be assigned the build-a-model-volcano project.

"So I did what anyone rational would do: I read about volcanoes. I learned a lot about the inside of the earth and what causes volcanoes. But I was basically left where started: I needed to build something that looked like a mountain and leaked red-hot liquid rock. So I needed some rock to melt (I figured any gravel would be good enough), a powerful enough heat source, and something capable of containing the heat source and directing the liquid rock.

"I ended up deciding to use an electric igniter to light a flare which then started combustion in some thermite. I decided to build the mountain out of sand, with a thin layer of quick-dry cement to hold it together. The base of the mountain curved up into a bowl to catch the molten rock. I figured the sand inside would slowly melt, but contain the thermite until it burnt out. And I put a steel pipe from the top of the mountain to the center where the gravel and thermite were. I also poured some water into the sand, figuring it would evaporate to provide enough pressure to move the molten rock out of the volcano and prevent the sand from melting for a while.

"On the day of the science fair, I asked the teacher, again, if this was really safe, and she said something affirmative but dismissive. That was the last time I trusted an adult to be responsible for anything important: I triggered the igniter from what I considered a safe distance. I'd never heard of a steam explosion before, but of course that didn't stop one from happening. The steel pipe embedded itself in the ceiling, and the thermite scattered and fell and set everything it touched on fire.

"Amazingly, everyone got out safely, and a fire engine arrived a few minutes later. They put out much of the fire, but unfortunately there were a few metal fires so when they sprayed then with water, everything got much worse. So they had to call for backup. Eventually they got it under control. I was later informed that my project was actually intended to involve reacting a weak acid with a weak base, which would have been harmless. I was apparently expected to know that somehow despite the complete lack of relevance to volcanoes.

"Afterwards the school sent out three pages of items that were now banned from the school. In the name of safety, of course. And again, everyone blamed me, even though I'd never brought or planned to bring a single item from their list. I mean, water guns and water balloons? Either they were already looking for an excuse, or the people working at muggle schools are the only people less sane than those working at magical schools. Or both.

"But the fire wasn't magical. It was absolutely 100% a natural chemical reaction," Harry concluded insistently.

"The aurors responded to an underage magic incident. They reported that the fire didn't look natural," George said.

"It looked like it was intended to do as much damage as possible, but left clear paths for everyone to escape," Fred added.

"They concluded that you clearly wanted that building gone, but didn't want anyone to get hurt."

"If you'd tried to hurt people, they'd probably have brought you back to be adopted into a magical family. Muggles wouldn't be able to deal with that safely."

"But they probably warned your parents to keep you away from that building if you ever got angry there."

"That... explains a lot, actually," Harry said thoughtfully.

"That it was a magical fire?"

"No, some stuff about how my parents acted after that."

"So you were the only wizard there, there was underage magic, and there was a big magic-looking fire. What do you expect us to believe?" Ron demanded suspiciously. Harry just glared at him.

"What if all of that is true?" Neville asked. "If the fire did start naturally but Harry's accidental magic controlled its spread. You might have saved everyone."

Ron scoffed loudly but Harry cut him off, "that's consistent with everything I know and what Fred and George said. But it's also something I'd really like to be true, so I'm biased toward believing it. I'll have to think about it later in more detail."

"Hermione, I hope you've seen how dangerous that fire-starter is and aren't planning on hanging around him so often now", Ron announced gravely.

"Ron, the fire was an accident and he probably saved everyone from it." Hermione calmly lectured.

"Yeah, according to HIM."

"Whatever. I'm going to the library." Hermione stated, thinking about how convenient it was that Ron wouldn't follow her to the place she'd intended to go before being pulled into this conversation.

"Yeah, me too" Harry called, getting up and following.

"What is WRONG with them?" Ernie asked, disgusted.

"Isn't it obvious?" Ron spat, "He's evil and he's turning her evil."

"I think she's always liked libraries, Ronnie" Fred started.

"And I think you like her. You're jealous aren't you?" George teased.

"Gah, I'm going... to the library" Ron announced, getting up. "Or somewhere more believable", he amended to the others, who were laughing hysterically.

[disclaimer: I have neither attempted nor done calculations on the science project described. Only an idiot would try it without doing careful analysis, having relevant prior experience, and having adequate safety precautions in place. That said, if anyone is inspired, please video and leave a hint to the Youtube link in the reviews (i.e. video oHg5SJYRHA0 is the first rickroll result for Youtube).]


	2. Falling or Flying

Chapter 25 act 3 3/4: Falling or Flying

Monday morning, Harry walked toward the Great Hall thinking about experiments he needed to perform. Conservation of energy is such an important law in physics; it has to hold for magic too. If he could calculate the energy mysteriously produced by different spells, maybe it correlates with the magical effort expended by those spells. Maybe he could quantify magical energy; measure how much he and others held. From there he could calculate the magical power a wizard absorbed from the environment. If it were a constant in a given location, it could be used to measure the local ambient magical field strength-

But this set of experiments had a flaw much like his first set: a beautiful plan of research based on a premise he had not yet tested, much less verified. He didn't intend to make that mistake twice.

"...looking forward to Hogsmeade. I need a break from..."

Most students talk about such trivial, boring things. It's a good thing he met Hermione when he did, despite how annoying she could be.

Hermione- Maybe Hermione was a poor choice of test subject for his initial magical experiments, due to her strong belief in the correctnessof the information in books. It shouldn't have mattered because she hadn't known the spells beforehand, but that was another assumption. Maybe the results would be different for someone who believed intent was the only important part of casting magic. Perhaps he should ask her to conduct a similar set of experiments around a different set of spells with himself as the test subject. Or maybe Draco would be interested...

"...finished your transfiguration homework yet? I don't get what Prof..."

Transfiguration. That's such a fascinating area of magic. He should really design a set of experiments to test its true abilities and limitations. Clearly, people could transfigure things without knowing every detail of what they were making. Could he transfigure something no one had made before (first priority: nanofactory)? More disturbingly, where was the intelligence that knew the details the wizard did not? What 'remembered' the original form and un-transfigured objects?

"...know you like Cedric. You should talk to..."

More pointless student conversations. So distracting. Anyway, hidden intelligences... maybe he should return to experimenting with his pouch; he had never come to a firm conclusion about how it worked, but it seemed to have at least some kind of rudimentary intelligence running it. Working with artificial intelligence could be very dangerous, and Harry doubted wizards had thought deeply about those ramifications. It could be important to quickly determine how far they had gotten.

"...going to jump off the tower, we should take feather-falling potions first..."

Maybe he'd start by listing magical objects, spells, etc. that required a hidden, non-trivial intelligence to- Wait, what?

Harry stopped and walked backward to where Dean Thomas and Seamus Finnegan where talking at the Gryffindor table. "...get feather-falling potion from Hogsmeade for us?"

"Excuse me", Harry began, "I thought I overheard a more interesting conversation than normal. You guys planning something fun?"

"Since when are you interested in anything besides reading and homework?", Dean asked. "You've never wanted to play anything before."

"Maybe he's planning to go to McGonagall or Sprout?", Seamus added. "Maybe he's hoping he can win some more precious house points."

Okay, he understood the homework comment, but when had he gotten a reputation as a snitch? The Gryffindors had all loved Harry after his first class with Snape. That sure hadn't lasted long.

Harry sighed. "Like I said, it sounded interesting. Something about maybe wanting feather-falling potion before jumping off a tower. That implies you intend to fly off the tower somehow, but want a safety in case something goes wrong. Maybe you found a spell for enchanting flying brooms? No, we fly every week anyway and you wouldn't need the tower." Harry thought for a moment while they waited, bemused. He continued, "You're not really going to fly, just fall. And primarily intend to use something besides the potion. I don't expect wizards would have many things like that when there are already flying brooms and feather-falling potions. But there are muggle things, like bungee cords, parachutes, and gliders." He saw surprise in their expressions, "gliders it is then. I'm in."

"Yeah, I was telling Seamus about muggle technology. He didn't believe they can fly. So we're going to try to transfigure a hang-glider."

"I'm still not convinced muggles can fly. So potions or no potions, you're going first."

"Yeah, it sounds like a lot of fun. I'm totally in", Harry repeated.

"And why, exactly should we let you tag along?", Seamus smirked.

"One, I have _feather-falling potion_ already", Harry pulled a vial out of his pouch and gestured with it as he continued. "Two, I know some third years who would probably be willing to help with the transfiguration. That would be a really big job for first years. And three, I have an aerodynamics book that, while it's mostly about airplane design, I'm pretty sure has a detailed picture of a hang-glider. And the equations to figure out some of the details." Harry paused. "You know what, I don't know why I should let you guys tag along with me."

"Let's not make any quick decisions", Dean said. "You've made some good points, but do you really think you can transfigure something that works right from just a picture in a book? I think we can work together on this."

"Playing with muggle flying machines?" Terry Boot asked, having heard a most of the conversation while standing nearby. "I expect crazy things like that from Gryffindors but from you... never mind."

"Well, then you're not invited", Dean said. He then stuck out his tongue at Terry.

Terry rolled his eyes and waved dismissively, "Like I would trust a muggle flying machine. And why? They can't be as good as brooms, so what's the point?"

Harry's mind marked this subject as boring and asked, "I've been wondering; how exactly does feather-falling potion work? What does it do? Maybe we should do a few experiments..."

"You're not worried about what will happen to the universe this time, Harry?", Terry smirked.

"How would a falling potion affect the universe, Terry? That's just silly", Harry answered, mentally adding, it's not like we're playing with time machines or anything. He continued, "I could tell you about the last time, but you'd have to be obliviated afterwards. That would make the whole thing moot, because then you'd be confused again. So rationally, so should just skip ahead and pretend we've already done that."

Dean and Seamus glanced at each other and frowned. "What do you mean, experiment?" asked Seamus.

"Does it reduce your terminal velocity or your acceleration or both? When does it start doing that? What happens if you take half a dose? We weight less than the average adults these potions are intended for. Do children fall more slowly or can we fall over a longer distance? How far can you use it to fall anyway? And how long will it still work after you take one: If I'd taken one during the first week, and hadn't fallen until now, would it still protect me?"

"Oh, they're good for about 30 minutes. I don't think there's a distance limit: I think you can fall for the whole 30 minutes if you start high enough. I don't know if anyone's done it though. I don't know about children; why would weight matter?" Seamus answered.

"To put it simply, it takes less effort to hold up light things than heavy things; that's what weight means. I haven't figured out the pattern for when size and weight matter to magic, so we should test this. Maybe give a dose to a small animal and drop it from a broom..."

"Hey, Kevin, mind if we give your cat a feather-falling potion", Dean called excitedly, snatching the potion vial from Harry and running a short distance over to Kevin Entwhistle. "We want to check something."

"That seems like a waste", Kevin responded. "Cats can already turn and land safely when they fall from most heights." His eyes widened as he continued, "unless you think the combination will make a cat fall up, roll upside-down, then fall down, then turn right-side-up again, repeating until it spins in place faster and faster."

"That sound like something muggles say about buttered toast attached to a cat's back", Harry interjected. "But it's a joke; the universe doesn't really work that way. Magic doesn't always respect common sense, but still... Never mind, I don't know what will happen; that's the point of testing things." That was all the encouragement Dean needed to empty the vial of feather-fall potion into the saucer of milk Kevin had prepared for his cat.

After it finished drinking a moment later, Kevin picked up the cat, then lowered his arms slowly. The cat did not follow. "Huh", said multiple students.

Harry looked at the cat, hovering a little over a meter off the ground, and started giggling uncontrollably, having thought of a fun way to renew his desired reputation, at least temporarily. The others looked on in confusion as Harry picked up a napkin, shook it open, and touched his wand to it. A few seconds later, he had a blue cat collar attached to a cat-sized red cape. He put the collar (which closed magnetically rather than using a physical latch; Harry had been planning to write his next transfiguration essay about the application of Topology to transfiguration safety) on the cat and then pushed it forward. The cat sailed along the Gryffindor table with a cape billowing behind it.

"You still think that was a waste of a potion?", Dean asked Kevin. Kevin shook his head without looking away from the cat.

"I so need to get a cape", Lavender announced to no one in particular.

"When and why would you wear a cape. That's just dumb", Parvati said firmly. Lavender just gave her an annoyed look before turning to watch the cat again.

After the cat flew for a few seconds, it panicked and twisted in the air such that it was flying feet-first. It spread out its body, quickly slowing down and dropping. When it neared the floor, it turned itself right-side-up and tried to run away. Unfortunately, during this attempt, it kicked off of the floor and shot across the room, quickly gaining altitude and loudly expressing its displeasure.

While the others were distracted watching the cat, Terry quietly backed away, sat at the Ravenclaw table, and loaded a plate with food, intending to pretend he had been there the whole time.

The cat turned again in time to safely 'land' and rebound off of a wall. It stopped yowling after it leveled out and hovered 10 meters above the ground. It shook its head then licked itself for a moment.

"We have to do something about this", Fred told George.

George nodded. "He's making us look bad. We have to do something really big."

"And soon", Fred concluded.

The cat was now staring intently at a nearby area of the Slytherin table, hanging at an odd angle and looking ready to pounce. Suddenly, it dove toward the table and grabbed a steak off of Draco's plate with its mouth. Without stopping, it took a few strides and jumped, overturning several plates and flying away. It landed on the opposite wall a moment later.

Draco slowly lowered his face into his hands, "Being friends with Harry can't be worth it. Can it?", he asked quietly.

"You'd think the scion of the great house of Malfoy would find friendship with the Boy-Who-Lived-And-Does-Weird-Things more valuable than some easily-replaced food", Daphne whispered to Tracey, rolling her eyes.

"Draco knows that", Tracey replied. "But he doesn't know that we know that. He's not an idiot. But he thinks everyone else is. He's not good at, um, modeling the way other people think. Or something."

"What?"

"It's something I overheard Harry say. I'm almost sure it applies here", Tracey answered.

"You _overhear_ a lot of what Harry says, don't you?", Daphne asked, amused.

Tracey attempted to act offended before they paused to watch as the cat dropped the steak, dove and caught it in midair, holding it between its forepaws and biting it while slowly drifting, upside-down, toward the center of the hall.

"I have a plan", Tracey said, quietly and ominously.

Daphne shook her head, "I'm going to regret asking. What?"

"When Professor Quirrell's extracurricular activities start up, I'm asking him to put me on Harry's team. We'll spend lots of time together then."

"Yeah, that's not going to happen, you'll be on Draco's team with all the other Slytherins."

"You know there won't be as many Ravenclaws and Hufflepuffs signed up as Slytherins and Gryffindors, so there'll be a Slytherin team led by Draco, a Gryffindor team led by someone, a Slytherclaw team led by Harry, and a Gryffinpuff team probably led by Susan. And you know how much Professor Quirrell likes Harry, so everyone who's enthusiastic about working with Harry will be on Harry's team."

"You might be right", Daphne said hesitantly. "I wonder if Professor Quirrell will let me join Susan's team. I don't think I could stand to work for Draco or Harry."

"Slytherins and Hufflepuffs working together? Daphne, that's just silly."

While the students watched the cat's antics, Professor McGonagall walked toward the Gryffindor table. Dean noticed her first and quietly nudged Harry. As Harry turned, she asked, "Mr. Potter, are you responsible for this?"

Harry decided that he was at least 60% responsible for everything that had happened, but that there was no point to implicating anyone else. He knew his best option for avoiding detentions and preserving house points would be to lose quickly, but there were more important things than mere house points. "Yes; I've discovered what happens when a cat takes a feather-falling potion. I assume you'd like to turn into a cat and try it? It looks really fun."

Seamus and Dean glanced at each other in surprise. McGonagall snapped, "No, Mr. Potter. I want you to resolve this situation, immediately."

"It's okay if you want to try it; that's what I'd be doing right now if I could turn into a cat. And you shouldn't worry about what the other professors will think. People are happier when they do fun things without worrying about being judged for them. There's a study-"

"Thank you for your opinion of my mental health, Mr. Potter", she said sarcastically. "Restrain the cat."

Harry shrugged mentally and raised his wand. "Wingardium leviosa." He caught the cat and directed it to Kevin, who reached out and held it. "Finite incantatem." Kevin moved his arms to support the cat's restored weight as the napkin slipped off its back to the floor.

"Twenty house points from Ravenclaw, and you'll be serving a detention with me after your last class today, Mr. Potter. Bring your textbooks."

"Oh, good. I've been meaning to ask you some questions about animagus stuff. This will give me a good opportunity."

She turned and walked away quickly, apparently pretending not to have heard. Harry thought he caught her lips twitch upward as she turned, but couldn't be sure.

"Thanks for covering for us; you're a real Gryffindor, Harry", Dean announced. They either missed or decided to ignore Harry's visible shudder.

"You seem much less upset than I would have thought. Getting in trouble and losing house points", Seamus added.

Harry shrugged, "when someone doesn't act the way you expect, it's evidence that your mental model of them is incomplete or incorrect."

They briefly looked confused, and Harry added "That was totally worth it."

Dean commented, "I can't believe she gave you a detention for that."

Harry shrugged again, "I don't really mind; I have to do homework some time. And Hogwarts is still better about things like that than my last school."

"What do you mean?"

"My last teacher had a rule: if something made me giggle for longer than fifteen seconds, I was supposed to assume there was a rule against it. Actually, any time I laughed, she usually made me stand in the corner and not touch anything for about fifteen minutes. Luckily the teachers here haven't implemented such an unpleasant and anti-intellectual policy. So, hang-gliding this weekend?"


End file.
